A known image forming apparatus forms an image with a decolorable toner that can be decolored by heat or a non-decolorable toner that cannot be decolored. Such an image forming apparatus generally fixes toner images to sheets at a low fixing temperature below the temperature at which the decolorable toner is not decolored when the image is printed with the decolorable toner since the fixing temperature for the decolorable toner and the fixing temperature for the non-decolorable toner are different. If the fixing process is performed on the image formed with the decolorable toner at a fixing temperature for the non-decolorable toner, there is a possibility that the image formed with the decolorable toner is decolored and becomes invisible. For this reason, the conventional image forming apparatus is designed to select either one of the decolorable toner and the non-decolorable toner having different fixing temperature to execute printing. There is a problem that the conventional image forming apparatus cannot print both the image with the decolorable toner and the image with the non-decolorable toner at the same time.